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vm: rework swap_pager_status to execute in constant time

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The lock-protected iteration is trivially avoidable.

This removes a serialisation point from Linux binaries (which end up calling
here from the sysinfo syscall).
This commit is contained in:
Mateusz Guzik 2020-06-09 14:16:18 +00:00
parent 4707401c75
commit 7ce3a31286
1 changed files with 3 additions and 9 deletions
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12
sys/vm/swap_pager.c
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@ -2541,16 +2541,10 @@ swapoff_all(void)
void
swap_pager_status(int *total, int *used)
{
struct swdevt *sp;
*total = 0;
*used = 0;
mtx_lock(&sw_dev_mtx);
TAILQ_FOREACH(sp, &swtailq, sw_list) {
*total += sp->sw_nblks;
*used += sp->sw_used;
}
mtx_unlock(&sw_dev_mtx);
*total = swap_total;
*used = swap_total - swap_pager_avail -
nswapdev * howmany(BBSIZE, PAGE_SIZE);
}
int